Fishing tool

ABSTRACT

A packer tool ( 10 ) for milling and retrieving a packer from the casing of a well bore is provided. The tool ( 10 ) comprises an upper milling portion ( 14 ), a lower attachment portion ( 16 ) at least partially located within the upper milling portion ( 14 ), and a debris retainer ( 28,128,228 ) for capturing milled cuttings within the tool ( 10 ). A method of milling and retrieving a packer using the tool is also provided.

PRIORITY CLAIM

This application claims the benefit of Great Britain patent application no. GB 0906934.5 filed Apr. 23, 2009, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a fishing tool for milling and retrieving a packer from a casing in an oil or gas well and in particular to a fishing tool which combines milling, retrieval and debris management in a single tool.

A packer is used to provide a seal within a casing of a well bore. When the seal is no longer required a milling and retrieval tool is typically used to remove the packer. These tools usually have an upper milling portion for milling or cutting through the slips which anchor the packer to the casing wall, and a lower attachment portion for picking up the remaining packer for transportation to the surface of the well.

The milled cuttings from the packer are circulated out of the well bore by the standard circulation of fluid down through the work string and up the annulus between the tool and the casing wall. Mud or pills of high viscosity fluid are typically used to assist in this debris removal.

As the debris is flushed up the outside of the tool, the packer can stick in the casing as the debris becomes trapped between the packer and the casing wall. When this occurs the packer can become disengaged from the retrieval tool and a further recovery procedure is required.

It is object of the present invention to provide a packer milling and retrieval tool which collects the milled cuttings from a packer being retrieved.

It is a further object of at least one embodiment of the present invention to provide a packer milling and retrieval tool that converts the flow from inside the work string to the outside of the work string and around the outside of the tool, so that milling cuttings are circulated up into the tool.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a packer tool comprising an upper milling portion, a lower attachment portion at least partially located within the upper milling portion, and a debris retainer for capturing milled cuttings within the tool.

The upper milling portion may comprise:

-   -   a sleeve which at least partially encloses the lower attachment         portion such that an annular chamber is defined between the         sleeve and the lower attachment portion; and     -   a mill provided on an open end of the sleeve.

The sleeve may have a closed end remote from the open end, and the debris retainer may comprise a filter portion which permits fluid flow from the annular chamber to the exterior of the tool.

The tool may further comprise one or more return flow ports which permit additional fluid flow from the annular chamber to the exterior of the tool.

The debris retainer may further comprise a strainer or filter located in the or each return flow port.

The debris retainer may further comprise a basket portion located within the annular chamber, the basket portion preventing any debris in the annular chamber from passing out of the open end of the sleeve. The debris retainer may further comprise a diverter plate located in the annular chamber and adapted to divert fluid flow in the chamber towards the basket portion. The basket portion may be formed from a plurality of biased finger members, the finger members being biased towards a closed position in which debris is prevented from passing out of the open end of the sleeve.

The debris retainer may further comprise one or more magnets located in the annular chamber.

The tool may further comprise:

-   -   a central bore extending axially through the tool; and     -   one or more flow diversion ports providing fluid communication         from the central bore to the exterior of the tool are located in         the tool to provide fluid flow from the central bore to the         outer surface of the tool.

The or each flow diversion port may include a nozzle to direct a jet of fluid out of the port.

The central bore may include a ball seat located downstream of the flow diversion ports. The ball seat may be shearable from the central bore.

According to a second aspect of the invention there is provided a method of retrieving a packer from a well bore, the method comprising the steps of:

-   -   (a) running a tool according to the first aspect of the         invention on a work string;     -   (b) engaging the lower attachment portion to the packer;     -   (c) milling the packer with the upper milling portion to free         the packer; and     -   (d) removing the work string from the well bore while retaining         milled cuttings in the debris retainer.

The method may further comprise the step of dropping a ball onto a ball seat in the tool so as to divert fluid flow from the work string through one or more flow diversion ports to the exterior of the tool.

The ball seat may be shearable and the method may further comprise increasing the pressure in the tool until the ball seat shears, thereby resuming fluid flow through the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompany drawings of which:

FIG. 1 is a cross-sectional view of a packer milling and retrieval tool according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view of a debris catching chamber of a packer milling and retrieval tool according to a second embodiment of the present invention;

FIG. 3 is a cross-sectional view of a debris catching chamber of a packer milling and retrieval tool according to a third embodiment of the present invention;

FIG. 4 is a cross-sectional view of a packer milling and retrieval tool according to the third embodiment, retrieving a packer from a casing;

FIG. 5 is a schematic representation of a packer milling and retrieval tool according to the present invention being deployed in a well bore; and

FIGS. 6 (a) and (b) are cross-sectional views and end view respectively of the tool of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Reference is initially made to FIG. 1 of the drawings which illustrates a packer milling and retrieval tool, generally indicated by reference numeral 10, according to a first embodiment of the present invention. Tool 10 comprises a mandrel 12 having an upper milling portion 14 and a lower attachment portion 16. Additionally, the tool has a chamber 18.

Tool 10 is shown in a casing 20 in a preferred orientation. Throughout the specification the terms upper and lower are used to refer to ends of the tool 10. It will be understood that the tool could equally find application in inclined or horizontal wells where the referencing is then used as appropriate.

Mandrel 12 has an upper end 22 including a threaded portion 24 for connection to a work string or drill string (not shown). Mandrel 12 includes a central bore 26 running axially through the centre of the tool 10. A sleeve 28 is arranged from a face 30 of the mandrel 12 around a slimmer portion 32 of the mandrel. As the face 30 is perpendicular to the bore 26, a chamber 18 is created by the annulus between the sleeve 28 and the slimmer portion 32 of the mandrel 12. At a lower end 34 of the sleeve 28 is arranged a mill 14. Mill 14 provides a cutting surface to anything arranged below it and around it. Such mills 14 are known to those skilled in the art. At a lower end 36 of the slimmer portion 32 of mandrel 12 is located retrieval means 16 which can attach to and pick up a packer (not shown). Retrieval means 16 are generally referred to as a stinger which includes a grapple or a collet arrangement which prevents the packer from falling off as it is retrieved. Such stingers are known in the art.

On the face 30 are arranged ports 38 connecting the chamber 18 to an outer surface 40 of the tool 10. Though the port 38 runs from the face 30 it may equally be positioned to run through the sleeve 28. Additionally sleeve 28 is formed of a cylindrical portion which is punctuated to provide a strainer or filter. Alternatively the sleeve 28 is a slotted tube. Thus fluid can pass from the chamber 18 to be filtered through the sleeve 28 or pass through the ports 38. Second ports 42 provide a passage for fluid from the central bore 26 to the outer surface 40 above the chamber 18. Preferably there are three ports 42 arranged equidistantly around the circumference of the tool 10. Each port 42 includes a jet nozzle 44 to provide in additional cleaning action when fluid exits the tool at the port 42.

A ball seat 55 is provided in the central bore at the top of the chamber 18. The ball seat 55 is best illustrated in FIG. 6. Like parts to those of FIG. 1 have been given the same reference numeral to aid clarity. Central bore 26 has a diameter 21 at the upper end 22. A ledge 27 is then provided to reduce the diameter. Further the bore is again narrowed gradually over length 25 and ends in a narrowed bore 23 through the slimmer portion 32. This arrangement ensures that drop ball 56, when inserted in bore 26 falls into the length 25 where it is secured and effectively blocks fluid flow through the bore 26. Fluid flow is then redirected through the three ports 42 which are located on ledge 27.

In use, tool 10 is connected to a work string and run into a casing 20. Reference is now made to FIG. 5 of the drawings which illustrates the tool 10 mounted on a work string 46 being run into the casing 20. Like parts to those of FIG. 1 have been given the same reference numeral to assist in clarity. During deployment fluid may be circulated through the tool through the central bore 26 around the base of the tool 36 and back up a annulus 48 created between the outer surface 40 of the tool 10 and the casing 20.

The tool 10 reaches a packer 50 which is set in the casing 20. The stinger 16 will insert into an aperture 52 centrally located in the packer 50. The tool 10 will further be run in until the mill 14 contacts packer 50 and by rotation of the tool 10, the packer is milled to release it from the casing 20. In particular, the slips 54 are milled through. As the packer 50 is milled, it is drawn into the chamber 18 so that the cuttings produced are released into the chamber 18.

As fluid flows through the central bore 26, this is difficult to maintain and a ball 56 is dropped through the central bore 26 while 56 comes to rest in the ball seat 55 and thus blocks the passage of fluid axially through the tool 10.

Fluid is now diverted in the direction shown in arrow A of FIG. 1 through the ports 42 and jetted out of the tool 10 by virtue of the nozzles 44. Fluid travels down hole in the annulus 48 and circulates back up into the chamber 18 shown in the direction of the arrows B in FIG. 1. Fluid now circulating in the direction of arrow B is laden with millings and other cuttings. These millings and cuttings are trapped on the sleeve 28 while filtered fluid can travel in the direction of arrow C in FIG. 1 and also through the port 38 in the direction of arrow D back to the outside of the tool. In this way only filtered well fluid passes back up the annulus 48 above the tool 10.

As the packer 50 is located within the chamber 18, it prevents cuttings or millings falling back down the well and into well fluid below the packer 50. While fluid circulation is maintained, the debris remains captured in the chamber 18 and can be brought to the surface. If, for some reason, the packer 50 becomes stuck during retrieval and the tool 10 has to be disengaged from the packer 50, the cuttings and millings remain in the tool by virtue of the circulation of the fluid and also by the assistance in the retention of the cuttings to magnets 58 arranged in the chamber 18.

Reference is now made to FIG. 2 of the drawings which illustrates a chamber 118 of a packer milling and retrieval tool in accordance with a second embodiment of the present invention. Like parts to those of FIG. 1 have been given the same reference numeral with the addition of 100. Tool 110 includes a milling portion and retrieval portion as detailed with reference to FIG. 1. However, for the tool 110 the chamber 118 now includes a diverter plate 60 and an internal basket 62. Diverter plate 60 is arranged at an upper end 62 of the chamber 118. Diverter plate 60 comprises a conical section arranged around the slimmer portion 132 of the mandrel 112. Basket 62 is arranged on an inner wall 64 of sleeve 128. Basket 62 comprises a strain or filter or may be a slotted liner.

In use, fluid travelling in direction B which is laden with millings or cuttings travels between the slimmer portion 132 and the basket 62. Fluid is redirected at the diverter 60 around the diverter in a torturous path shown in arrow E. In making the torturous path, the cuttings and millings fall out of the flow due to the reduction in pressure in taking a longer path. Cuttings and millings then fall back in the direction of arrow F into the basket 62. Well fluid free of the cuttings can then travel out of the tool 110 via the ports 138 in an identical manner to the tool of FIG. 1.

This embodiment has the advantage that if the packer becomes detached at any point and fluid flow and circulation is stopped, collected cuttings will remain in the basket 62 within the chamber 118 for retrieval to the surface.

Reference is now made to FIGS. 3 and 4 of the drawings which illustrates a third embodiment of a packer milling and retrieval tool, generally indicated by reference numeral 210. Like parts to those of FIG. 1 have been given the same reference numeral but with the addition of 200. Tool 210 includes a packer retrieval portion 216 and a milling portion 214 as described with reference to the first embodiment. In this embodiment, chamber 218 now includes fingers 66 at a lower end 68 and a strainer 70 at the upper end 262.

As shown in FIG. 4, in use, the tool 210 mills the packer 250 using the milling elements 214 while the retrieval means 216 engages the packer 250. The packer 250 is swallowed into an annulus 72 between the sleeve 228 and the slimmer portion 232. Referring back to FIG. 3, the well fluid laden with cuttings is forced up in the direction of arrows B into the chamber 218. To enter the chamber the well fluid forces the fingers 66 upwards by virtue of springs 74 arranged on the sleeve 228. The fingers 66 will remain in an upright and open position while fluid flows into the chamber 218. Fluid exits the chamber by passing through the strainer 70 and out of the port 238. Millings and cuttings are prevented from taking this path by the strainer 70. Strainer 70 is a conical strainer covering the upper end 262 of the chamber 218.

When the tool 210 is pulled from the well, the cuttings and millings 76 will fall from the strainer 70 back down the chamber 218. As fluid flow is now no longer in the direction of arrow B, the fingers 66 will drop closing the lower end 68 of the chamber 218. This will provide a basket 78 at the lower end 68 of the chamber to retain the cuttings 76 as the tool is brought to the surface.

The principal advantage of the present invention is that it provides a tool which captures cuttings and millings in a packer milling and retrieval tool. As the tool converts the flow from inside the work string to the outside of the work string and around the outer diameter of the tool, millings and cuttings are circulated up into the tool instead of around the outside of the tool and thus the cuttings are captured and retained in the tool.

A further advantage of the tool is that if the packer is lost for some reason i.e. if the packer becomes stuck in the hole and the tool needs to be disengaged from the packer, then the cuttings are retained in the tool rather than dumped.

A yet further advantage of the present invention is that by dropping a ball into the central bore, fluid flow can be selectively diverted from the tool to the annulus between the tool and the casing. This provides a cross-over tool and allows reverse circulation through the tool in the casing. Flow can be re-routed back down the central bore if the ball seat is shearable as is known in the art.

Various modifications may be made to the invention herein described without departing from the scope thereof. For example, whilst each of the preferred embodiments described herein includes a central bore for axial fluid flow through the tool the bore is a preferable, rather than essential, feature. The tool can be provided without a central bore and diversion ports if preferred. 

1. A packer tool comprising an upper milling portion, a lower attachment portion at least partially located within the upper milling portion, and a debris retainer for capturing milled cuttings within the tool.
 2. A tool according to claim 1, wherein the upper milling portion comprises: a sleeve which at least partially encloses the lower attachment portion such that an annular chamber is defined between the sleeve and the lower attachment portion; and a mill provided on an open end of the sleeve.
 3. A tool according to claim 2, wherein the sleeve has a closed end remote from the open end, and the debris retainer comprises a filter portion which permits fluid flow from the annular chamber to the exterior of the tool.
 4. A tool according to claim 2 and further comprising one or more return flow ports which permit additional fluid flow from the annular chamber to the exterior of the tool.
 5. A tool according to claim 4, wherein the debris retainer further comprises a strainer or filter located in the or each return flow port.
 6. A tool according to claim 2, wherein the debris retainer further comprises a basket portion located within the annular chamber, the basket portion preventing any debris in the annular chamber from passing out of the open end of the sleeve.
 7. A tool according to claim 6, wherein the debris retainer further comprises a diverter plate located in the annular chamber and adapted to divert fluid flow in the chamber towards the basket portion.
 8. A tool according to claim 6, wherein the basket portion is formed from a plurality of biased finger members, the finger members being biased towards a closed position in which debris is prevented from passing out of the open end of the sleeve.
 9. A tool according to claim 2, wherein the debris retainer further comprises one or more magnets located in the annular chamber.
 10. A tool according to claim 1 and further comprising: a central bore extending axially through the tool; and one or more flow diversion ports providing fluid communication from the central bore to the exterior of the tool are located in the tool to provide fluid flow from the central bore to the outer surface of the tool.
 11. A tool according to claim 10, wherein the or each flow diversion port includes a nozzle to direct a jet of fluid out of the port.
 12. A tool according to claim 10 wherein the central bore includes a ball seat located downstream of the flow diversion ports.
 13. A tool according to claim 12, wherein the ball seat is shearable from the central bore.
 14. A method of retrieving a packer from a well bore, the method comprising the steps of: (a) running a tool according to claim 1 on a work string; (b) engaging the lower attachment portion to the packer; (c) milling the packer with the upper milling portion to free the packer; and (d) removing the work string from the well bore while retaining milled cuttings in the debris retainer.
 15. A method according to claim 14, and further comprising the step of dropping a ball onto a ball seat in the tool so as to divert fluid flow from the work string through one or more flow diversion ports to the exterior of the tool.
 16. A method according to claim 15, wherein the ball seat is shearable and the method further comprises increasing the pressure in the tool until the ball seat shears, thereby resuming fluid flow through the tool. 